1. Field of the Invention
The present invention relates generally to feed horns and more particularly, to a radome for a feed horn and an assembly of a feed horn and a radome.
2. Description of the Related Art
A feed horn is a component of a signal transmission device, such as a satellite television antenna, for receiving signals of one or a plurality of frequency bands and feeding the signals to a signal processor and then to a client device. Alternatively, the feed horn can be used reversely to send out processed signals of one or a plurality of frequency bands.
In some cases, such as Taiwan Patent No. I223467, an opening of the feed horn is covered by a radome. In general, the radome for the feed horn has only functions of water resistance and blocking out foreign objects, and may have a disadvantage of deteriorating the performance of the feed horn in receiving and sending signals. A radome for a high-grade feed horn has a specific design that a surface of the radome is perpendicular to advancing directions of electric waves passing through the feed horn. However, the aforesaid specific design of the radome can improve the performance of the feed horn in receiving and sending signals slightly. To minimize the interference from the radome in electric-waves transmission of the feed horn, the conventional radome for the feed horn is designed to be very thin in its thickness; therefore the conventional radome is difficult in manufacturing and liable to be damaged.
In some cases, such as U.S. Pat. No. 3,413,642 and No. 3,754,273, the feed horn is provided with a plurality of circular side-lobe-reducing corrugations protruding or concaved from an inner surface of the feed horn to reduce edge diffraction occurring at the peripheral of the opening of the feed horn and lowering the isolation of cross polarization waves and co-polarization waves. However, the side-lobe-reducing corrugations are made integrally at the inner surface of the feed horn, resulting in difficulties in manufacturing.
Alternatively, the feed horn might be provided with a plurality of side-lobe-reducing corrugations extending from an outer surface of the feed horn and surrounding the opening of the feed horn in a concentric circle manner. For example, Taiwan Patent No. I223469 disclosed a feed horn having two side-lobe-reducing corrugations surrounding an opening of the feed horn. This kind of side-lobe-reducing corrugations located at the outer surface is more easily made than the aforesaid side-lobe-reducing corrugations located at the inner surface; however, the feed horn with such design may have a big size, resulting in inconvenience in application. Besides, this kind of feed horn usually has at least two side-lobe-reducing corrugations for good performance in reducing side lobes; the more side-lobe-reducing corrugations the feed horn has, the larger the feed horn is. In particular, for the feed horn having a plurality of channels for receiving signals of a plurality of frequency bands, each of the channels should be provided with at least two side-lobe-reducing corrugations surrounding an opening thereof so that the feed horn is very large in dimension and very inconvenient in application.